Mix dry ingredients. In a separate bowl mix the eggs, oil, zucchini, and orange peel. Combine. Add chopped walnuts if desired. Pour into buttered 9-inch loaf pan. (I prefer to skip the walnuts and sprinkle sliced almonds on top of the bread. They toast while baking and are the perfect touch!) Bake at a preheated oven at 375 degrees for about 50 minutes. Let cook 5 minutes in pan, and then turn out onto cooling rack.